Leaky pipes or condensation? This 48-hour test will tell you for sure

Damp spots on walls are often mistaken for condensation caused by poor ventilation, when the actual cause may be a hidden leak within the structure. Residents can distinguish between surface moisture and structural damage using a simple foil screen test. This method uses aluminum foil as a vapor barrier. By sealing a section of the wall, the surface is isolated from the indoor air, creating a closed system that removes the influence of room temperature and humidity. If moisture appears on the inner side of the foil, the side touching the wall, the water is migrating from inside the structure, suggesting a pipe leak or capillary rise. If the foil remains dry, the wall is simply "sweating" because warm, humid indoor air is hitting a cold surface.